In recent years it has become evident that some types of antidepressants are associated both with an increased risk of falling and decreased bone mineral density. These factors predispose patients for serious fractures such as hip fractures with substantial morbidity and mortality. The specific mechanisms involved in this negative impact on bone and postural control have not been fully elucidated. It is well known that Vitamin D plays an important role for bone health as well as muscle function and thus indirectly postural control. Furthermore, vitamin D deficiency has been observed among depressed patients. To our knowledge no study has investigated the involvement of Vitamin D in relation to the increased risk of fractures associated with antidepressants. Therefore, this project will investigate the underlying mechanisms leading to skeletal impairment and musculoskeletal symptoms in patients receiving different types of antidepressants. Moreover, the effect of vitamin D supplementation will be investigated among patients taking these antidepressants.